1. Field of the Invention
The present invention relates to an impact assembly, and more particularly to an impact assembly for a power tool that prevents stripping heads of bolts and nuts.
2. Description of Related Art
Conventional power tools are used to tighten or loosen bolts and nuts, and usually comprise single or dual impact assemblies.
With reference to FIG. 9, a conventional impact assembly (50) for a power tool in accordance with the prior art comprises a hammer frame (51), two hammer pins (53), two hammers (52) and an output axle (60). The hammer frame (51) is mounted in the power tool and is connected to and rotated by a rotary driver of the power tool. The hammer pins (53) are parallelly mounted in the hammer frame (51). The hammers (52) are mounted in the hammer frame (51) and respectively engage the hammer pins (53) and each hammer (52) has a center, an engaging hole (521) and two impact protrusions (522). The engaging hole (521) is defined through the center of the hammer (52) and has an inner surface. The impact protrusions (522) are formed on the inner surface of the engaging hole (521) in the hammer (52). The output axle (60) is mounted in the hammer frame (51) and is disposed through the engaging holes (521) in the hammers (52) and has an external surface and two anvils (61). The anvils (61) are formed on the external surface of the output axle (60) and correspond to the impact protrusions (522) in the engaging holes (521) of the hammers (52).
When the conventional power tool is used, the rotary driver is rotated to drive the hammer frame (51) to rotate. Because the hammer pins (53) are connected between the hammer frame (52) and the hammers (52), the hammers (52) will rotate with the hammer (51). The impact protrusions (522) in the engaging holes (521) of the hammers (52) respectively engage the anvils (61) on the output axle (60) synchronously. Consequently, the output axle (60) will be driven to rotate with the hammer frame (51) at high intermittent torque. A tool head sleeve is further mounted on the output axle (60) to loosen the fastener.
When changing or maintaining a vehicle wheel, the conventional power tool is implemented, having a same or higher maximum pounds of torque than specifications or regulations regarding the fastener, to adjust the bolts and nuts. The conventional power tool is operated several times to adjust the bolts and nuts to correct specifications and when tightening, this may cause the head to be over-torqued and stripped. Furthermore, since the power tool delivers an unknown torque, when tightening the fastener, the fastener may not meet safety standards, laws or regulations for each country.
To overcome the shortcomings, the present invention tends to provide an impact assembly to mitigate or obviate the aforementioned problems.